cleanups: ensure that git-compat-util.h is included first

CodingGuidelines states that the first #include in C files should be
git-compat-util.h or another header file that includes it, such as
cache.h or builtin.h.

Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/sigchain.c b/sigchain.c
index 1118b99..faa375d 100644
--- a/sigchain.c
+++ b/sigchain.c
@@ -1,5 +1,5 @@
-#include "sigchain.h"
 #include "cache.h"
+#include "sigchain.h"
 
 #define SIGCHAIN_MAX_SIGNALS 32